Pressure sensing guidewires

ABSTRACT

Medical devices and methods for making and using medical devices are disclosed. An example medical device may include a medical device for measuring blood pressure. The medical device may include an elongated shaft having a proximal region and a distal region. An optical fiber may extend along the proximal region. The optical fiber may be secured to an inner surface of the shaft. An optical pressure sensor may be coupled to the optical fiber. The optical pressure sensor may be disposed along the distal region. A sealing member may be attached to the optical fiber and may have a surface engaged with the inner surface of the shaft.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 to U.S.Provisional Application Ser. No. 62/088,334, filed Dec. 5, 2014, theentirety of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure pertains to medical devices, and methods formanufacturing medical devices. More particularly, the present disclosurepertains to blood pressure sensing guidewires and methods for usingpressure sensing guidewires.

BACKGROUND

A wide variety of intracorporeal medical devices have been developed formedical use, for example, intravascular use. Some of these devicesinclude guidewires, catheters, and the like. These devices aremanufactured by any one of a variety of different manufacturing methodsand may be used according to any one of a variety of methods. Of theknown medical devices and methods, each has certain advantages anddisadvantages. There is an ongoing need to provide alternative medicaldevices as well as alternative methods for manufacturing and usingmedical devices.

BRIEF SUMMARY

This disclosure provides design, material, manufacturing method, and usealternatives for medical devices. An example medical device may includea medical device for measuring blood pressure. The medical device maycomprise:

an elongated shaft having a proximal region and a distal region;

an optical fiber extending along the proximal region;

wherein the optical fiber is secured to an inner surface of the shaft;

an optical pressure sensor coupled to the optical fiber, the opticalpressure sensor being disposed along the distal region; and

a sealing member attached to the optical fiber and having a surfaceengaged with the inner surface of the shaft.

Alternatively or additionally to any of the embodiments above, themedical device further comprises a centering member coupled to theoptical fiber and positioned adjacent to the optical pressure sensor.

Alternatively or additionally to any of the embodiments above, thesealing member is secured to a proximal end of the centering member.

Alternatively or additionally to any of the embodiments above, thesealing member includes a conical portion.

Alternatively or additionally to any of the embodiments above, theconical portion is wedged against the inner surface of the shaft.

Alternatively or additionally to any of the embodiments above, thesealing member includes a cylindrical section.

Alternatively or additionally to any of the embodiments above, thecylindrical section contacts the inner surface of the shaft.

Alternatively or additionally to any of the embodiments above, whereinthe optical fiber is secured to the inner surface of the shaft with anadhesive.

Alternatively or additionally to any of the embodiments above, whereinthe shaft includes an outer coating.

Alternatively or additionally to any of the embodiments above, thesealing member is designed to limit distal migration of the coatingwithin the shaft.

Alternatively or additionally to any of the embodiments above, the shafthas a plurality of slots formed therein.

Alternatively or additionally to any of the embodiments above, thedistal region of the shaft has a distal inner diameter, wherein theproximal region of the shaft has a proximal inner diameter, and whereinthe distal inner diameter is larger than the proximal inner diameter.

Alternatively or additionally to any of the embodiments above, thesealing member is positioned at a transition region between the proximalregion and the distal region.

Alternatively or additionally to any of the embodiments above, themedical device is a guidewire for measuring fractional flow reserve.

Another example medical device may include a medical device formeasuring blood pressure. The medical device comprises:

a tubular member having a proximal region and a distal region;

a coating disposed along an outer surface of the tubular member;

wherein the tubular member has a plurality of slots formed therein;

an optical fiber extending along the proximal region;

an optical pressure sensor coupled to the optical fiber, the opticalpressure sensor being disposed along the distal region; and

a sealing member attached to the optical fiber and having a surfaceengaged with the inner surface of the tubular member so as to limitdistal migration of the coating within the tubular member.

Alternatively or additionally to any of the embodiments above, thesealing member includes a conical portion that is wedged against theinner surface of the tubular member.

Alternatively or additionally to any of the embodiments above, thesealing member includes a cylindrical section that contacts the innersurface of the tubular member.

Alternatively or additionally to any of the embodiments above, themedical device further comprises a centering member coupled to theoptical fiber and positioned adjacent to the optical pressure sensor andwherein the sealing member is secured to a proximal end of the centeringmember.

Alternatively or additionally to any of the embodiments above, thedistal region of the tubular member has a distal inner diameter, whereinthe proximal region of the tubular member has a proximal inner diameter,wherein the distal inner diameter is larger than the proximal innerdiameter, and wherein the sealing member is positioned at a transitionregion between the proximal region and the distal region.

Methods are also disclosed. An example method may include a method formanufacturing a medical device. The method comprises:

disposing an optical fiber within a tubular member, wherein:

-   -   a coating is disposed along an outer surface of the tubular        member,    -   the tubular member has a proximal region and a distal region,    -   the distal region has a distal inner diameter,    -   the proximal region has a proximal inner diameter that is        smaller than the distal inner diameter,    -   the distal region, the proximal region, or both have a plurality        of slots formed therein, and    -   an optical pressure sensor coupled to the optical fiber, the        optical pressure sensor being disposed within the distal region        of the tubular member;

disposing a sealing member within the tubular member, the sealing memberhaving a surface engaged with an inner surface of the tubular member;and

wherein the sealing member is designed to limit distal migration of thecoating within the tubular member.

Alternatively or additionally to any of the embodiments above, thesealing member has a conical portion and wherein disposing a sealingmember within the tubular member includes wedging the conical portion ofthe sealing member against the inner surface of the tubular member.

The above summary of some embodiments is not intended to describe eachdisclosed embodiment or every implementation of the present disclosure.The Figures, and Detailed Description, which follow, more particularlyexemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of thefollowing detailed description in connection with the accompanyingdrawings, in which:

FIG. 1 is a partial cross-sectional side view of a portion of an examplemedical device;

FIG. 2 is a partial cross-sectional view of an example medical devicedisposed at a first position adjacent to an intravascular occlusion;

FIG. 3 is a partial cross-sectional view of an example medical devicedisposed at a second position adjacent to an intravascular occlusion;

FIG. 4 is a partial cross-sectional side view of a portion of an examplemedical device;

FIG. 5 is a partial cross-sectional side view of a portion of an examplemedical device; and

FIG. 6 is a partial cross-sectional side view of a portion of an examplemedical device.

While the disclosure is amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit the invention tothe particular embodiments described. On the contrary, the intention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the disclosure.

DETAILED DESCRIPTION

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere inthis specification.

All numeric values are herein assumed to be modified by the term“about,” whether or not explicitly indicated. The term “about” generallyrefers to a range of numbers that one of skill in the art would considerequivalent to the recited value (i.e., having the same function orresult). In many instances, the terms “about” may include numbers thatare rounded to the nearest significant figure.

The recitation of numerical ranges by endpoints includes all numberswithin that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and5).

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

It is noted that references in the specification to “an embodiment”,“some embodiments”, “other embodiments”, etc., indicate that theembodiment described may include one or more particular features,structures, and/or characteristics. However, such recitations do notnecessarily mean that all embodiments include the particular features,structures, and/or characteristics. Additionally, when particularfeatures, structures, and/or characteristics are described in connectionwith one embodiment, it should be understood that such features,structures, and/or characteristics may also be used connection withother embodiments whether or not explicitly described unless clearlystated to the contrary.

The following detailed description should be read with reference to thedrawings in which similar elements in different drawings are numberedthe same. The drawings, which are not necessarily to scale, depictillustrative embodiments and are not intended to limit the scope of theinvention.

During some medical interventions, it may be desirable to measure and/ormonitor the blood pressure within a blood vessel. For example, somemedical devices may include pressure sensors that allow a clinician tomonitor blood pressure. Such devices may be useful in determiningfractional flow reserve (FFR), which may be understood as the pressureafter a stenosis relative to the pressure before the stenosis (and/orthe aortic pressure).

FIG. 1 illustrates a portion of an example medical device 10. In thisexample, medical device 10 is a blood pressure sensing guidewire 10.However, this is not intended to be limiting as other medical devicesare contemplated including, for example, catheters, shafts, leads,wires, or the like. Guidewire 10 may include a tubular member or shaft12. Shaft 12 may include a proximal portion 14 and a distal portion 16.The materials for proximal portion 14 and distal portion 16 may vary andmay include those materials disclosed herein or known in the art. Forexample, distal portion 16 may include anickel-cobalt-chromium-molybdenum alloy (e.g., MP35-N). Proximal portion14 may include stainless steel. These are just examples. Other materialsmay also be utilized.

In some embodiments, proximal portion 14 and distal portion 16 areformed from the same monolith of material. In other words, proximalportion 14 and distal portion 16 are portions of the same tube definingshaft 12. In other embodiments, proximal portion 14 and distal portion16 are separate tubular members that are joined together. For example, asection of the outer surface of portions 14/16 may be removed and asleeve 17 may be disposed over the removed sections to join portions14/16. Alternatively, sleeve 17 may be simply disposed over portions14/16. Other bonds may also be used including welds, thermal bonds,adhesive bonds, or the like. If utilized, sleeve 17 used to joinproximal portion 14 with distal portion 16 may include a material thatdesirably bonds with both proximal portion 14 and distal portion 16. Forexample, sleeve 17 may include a nickel-chromium-molybdenum alloy (e.g.,INCONEL).

A plurality of slots 18 may be formed in shaft 12. In at least someembodiments, slots 18 are formed in distal portion 16. In at least someembodiments, proximal portion 14 lacks slots 18. However, proximalportion 14 may include slots 18. Slots 18 may be desirable for a numberof reasons. For example, slots 18 may provide a desirable level offlexibility to shaft 12 (e.g., along distal portion 16) while alsoallowing suitable transmission of torque. Slots 18 may bearranged/distributed along distal portion 16 in a suitable mannerincluding any of those arrangements disclosed herein. For example, slots18 may be arranged as opposing pairs of slots 18 that are distributedalong the length of distal portion 16. In some embodiments, adjacentpairs of slots 18 may have a substantially constant spacing relative toone another. Alternatively, the spacing between adjacent pairs may vary.For example, more distal regions of distal portion 16 may have adecreased spacing (and/or increased slot density), which may provideincreased flexibility. In other embodiments, more distal regions ofdistal portion 16 may have an increased spacing (and/or decreased slotdensity). These are just examples. Other arrangements are contemplated.

A pressure sensor 20 may be disposed within shaft 12 (e.g., within alumen 22 of shaft 12). While pressure sensor 20 is shown schematicallyin FIG. 1, it can be appreciated that the structural form and/or type ofpressure sensor 20 may vary. For example, pressure sensor 20 may includea semiconductor (e.g., silicon wafer) pressure sensor, piezoelectricpressure sensor, a fiber optic or optical pressure sensor, a Fabry-Perottype pressure sensor, an ultrasound transducer and/or ultrasoundpressure sensor, a magnetic pressure sensor, a solid-state pressuresensor, or the like, or any other suitable pressure sensor.

As indicated above, pressure sensor 20 may include an optical pressuresensor. In at least some of these embodiments, an optical fiber or fiberoptic cable 24 (e.g., a multimode fiber optic) may be attached topressure sensor 20 and may extend proximally therefrom. An attachmentmember 26 may attach fiber optic cable 24 to shaft 12. Attachment member26 may include an adhesive member or bond that is circumferentiallydisposed about and attached to fiber optic cable 24 and may be securedto the inner surface of shaft 12 (e.g., distal portion 16). In at leastsome embodiments, attachment member 26 is proximally spaced frompressure sensor 20. Other arrangements are contemplated.

In at least some embodiments, distal portion 16 may include a regionwith a thinned wall and/or an increased inner diameter that defines ahousing region 52. In general, housing region 52 is the region of distalportion 16 that ultimately “houses” the pressure sensor (e.g., pressuresensor 20). By virtue of having a portion of the inner wall of shaft 12being removed at housing region 52, additional space may be created orotherwise defined that can accommodate sensor 20.

In at least some embodiments, it may be desirable for pressure sensor 20to have reduced exposure along its side surfaces to fluid pressure(e.g., from the blood). Accordingly, it may be desirable to positionpressure sensor 20 along a landing region 50 defined along housingregion 52. Landing region 50 may be substantially free of slots 18 sothat the side surfaces of pressure sensor 20 have a reduced likelihoodof being deformed due to fluid pressures at these locations. Distal oflanding region 50, housing region 52 may include slots 18 that providefluid access to pressure sensor 20.

Moreover, one or more of slots 18 may define a fluid pathway that allowsblood (and/or a body fluid) to flow from a position along the exterioror outer surface of guidewire 10 (and/or shaft 12), through slots 18,and into the lumen 22 of shaft 12, where the blood can come into contactwith pressure sensor 20. Because of this, no additional sideopenings/holes (e.g., other than one or more slots 18, a single slot 18extending through the wall of shaft 12, and/or a dedicated pressure portor opening) may be necessary in shaft 12 for pressure measurement. Thismay also allow the length of distal portion 16 to be shorter thantypical sensor mounts or hypotubes that would need to have a lengthsufficient for a suitable opening/hole (e.g., a suitable “large”opening/hole) to be formed therein that provides fluid access to sensor20.

A tip member 30 may be coupled to distal portion 16. Tip member 30 mayinclude a shaping member 32 and a spring or coil member 34. A distal tip36 may be attached to shaping member 32 and/or spring 34. In at leastsome embodiments, distal tip 36 may take the form of a solder ball tip.Tip member 30 may be joined to distal portion 16 of shaft 12 with abonding member 46 such as a weld.

Shaft 12 may include a hydrophilic coating 19. In some embodiments,hydrophilic coating 19 may extend along substantially the full length ofshaft 12. In other embodiments, one or more discrete sections of shaft12 may include hydrophilic coating 19.

In use, a clinician may use guidewire 10 to measure and/or calculate FFR(e.g., the pressure after an intravascular occlusion relative to thepressure before the occlusion and/or the aortic pressure). Measuringand/or calculating FFR may include measuring the aortic pressure in apatient. This may include advancing guidewire 10 through a blood vesselor body lumen 54 to a position that is proximal or upstream of anocclusion 56 as shown in FIG. 2. For example, guidewire 10 may beadvanced through a guide catheter 58 to a position where at least aportion of sensor 20 is disposed distal of the distal end of guidecatheter 58 and measuring the pressure within body lumen 54. Thispressure may be characterized as an initial pressure. In someembodiments, the aortic pressure may also be measured by another device(e.g., a pressure sensing guidewire, catheter, or the like). The initialpressure may be equalized with the aortic pressure. For example, theinitial pressure measured by guidewire 10 may be set to be the same asthe measured aortic pressure. Guidewire 10 may be further advanced to aposition distal or downstream of occlusion 56 as shown in FIG. 3 and thepressure within body lumen 54 may be measured. This pressure may becharacterized as the downstream or distal pressure. The distal pressureand the aortic pressure may be used to calculate FFR.

It can be appreciated that an FFR system that utilizes an opticalpressure sensor in a pressure sensing guidewire may be navigated throughthe tortuous anatomy. This may include crossing relatively tight bendsin the vasculature. Because of this, and for other reasons, it may bedesirable of pressure sensing guidewire to be relatively flexible, forexample adjacent to the distal end. It can be appreciated that inrelatively flexible guidewires, bending the guidewire could result incontact between an inner surface of the guidewire and, for example, thepressure sensor. Such contact could lead to alterations and/ordeformations of the pressure sensor, potentially leading to pressurereading offsets. Disclosed herein are pressure-sensing guidewires withincreased flexibility. Furthermore, the guidewires disclosed herein mayalso include structural features that may help to reduce contact betweenthe pressure sensor and the inner surface of the guidewire and,therefore, help to reduce the possibility of pressure reading offsets.

FIG. 4 illustrates a portion of another example guidewire 110 that maybe similar in form and function to other guidewires disclosed herein.Guidewire 110 may include shaft 112 having proximal portion 114 anddistal portion 116. Distal portion 116 may have slots or slits 118formed therein. In some instances, at least some of slits 118 extendthrough only a portion of the wall of shaft 112. In some of these and inother instances, at least some of slits 118 extend all the way throughthe wall of shaft 112. Pressure sensor 120 may be disposed within shaft112. In at least some embodiments, pressure sensor 120 may be an opticalpressure sensor having optical fiber 124 coupled thereto. A slot oropening (not shown) may be formed in distal portion 116 so as to allowfluid (e.g., blood) to access sensor 120.

A centering member 160 may be coupled to optical fiber 124. In general,centering member 160 may be disposed along distal portion 116 of shaft112 and may define a location where contact may occur with the innersurface of shaft 112. More particularly, when shaft 112 is bent,deflected, or otherwise deformed, the outer surface of centering member160 may come into contact with the inner surface of shaft 112. In doingso, centering member 160 may reduce the likelihood that inner surface ofshaft 112 may contact pressure sensor 120. Therefore, by includingcentering member 160, guidewire 110 may be less likely to have pressurereading offsets.

In at least some embodiments, centering member 160 may be positionedadjacent to pressure sensor 120. For example, centering member 160 maybe spaced a distance D from the proximal end of pressure sensor 120.Distance D may be on the order of about 0.5-20 mm, or about 1-10 mm,about 1-5 mm, or about 2-5 mm. These are just examples. Other distancesare contemplated. In other embodiments, centering member 160 may bepositioned adjacent the distal end of pressure sensor 120.

The form of centering member 160 may vary. In some instances, centeringmember 160 may be a polymer member coupled to optical fiber 124. Thepolymer may include any of the polymers disclosed herein (e.g.,polyimide). The shape or form of centering member 160 may also vary. Forexample, centering member 160 may take the form of a cylindrical diskcoupled to optical fiber 124. However, a number of other shapes,lengths, and forms are contemplated. This may include centering members160 with a substantially circular cross-sectional shape, with anon-circular cross-sectional shape, or the like. The number of centeringmembers 160 may also vary. In some embodiments, only one centeringmember 160 may be utilized. In other embodiments, two, three, four,five, six, or more centering members 160 may be utilized. The centeringmember(s) 160 may be arranged in a variety of different locations(proximal, distal, immediately adjacent, etc.) relative to pressuresensor 120.

FIG. 5 illustrates another example guidewire 210 that may be the same inform and function to other guidewires disclosed herein. Guidewire 210includes shaft 212 having proximal region 214 and distal region 216.Shaft 212 has slots 218 formed therein. Optical sensor 220 is disposedwithin distal region 216. In at least some instances, a slot or opening(not shown) may be formed in distal region 216 so as to allow fluid(e.g., blood) to access sensor 220. Fiber optic cable 224 is secured tooptical sensor 220 and extends proximally therefrom. Centering member260 may be secured to fiber optic cable 224.

Fiber optic cable 224 may be attached to shaft 212 with attachmentmember 226. In some instances, attachment member 226 takes the form ofan adhesive that is applied to fiber optic cable 224 through slot 218 a.Adhesive 226 bonds to fiber optic cable 224 and to the inner surface ofshaft 212, thereby securing the position of fiber optic cable 224relative to shaft 212. In some instances, attachment of fiber opticcable 224 to shaft 212 is not necessary such that guidewire 210 lacksattachment member 226.

A coating 219 may be disposed along the outer surface of shaft 212. Insome instances, coating 219 extends along substantially the full lengthof shaft 212. In other instances, coating 219 extends along only aportion of the length of shaft 212. In still other instances, coating219 is arranged as a plurality of discrete coating sections disposedalong shaft 212. Coating 219 may include a hydrophilic material, alubricious material, or the like.

When coating 219 is applied to shaft 212, coating 219 could migratedistally within shaft 212. It is possible that coating 219 could migrateto a position adjacent to sensor 220. This may include coming intocontact with sensor 220. It may be desirable to limit distal migrationof coating 219 within shaft 212. For example, migration of coating 219to a position adjacent to or in contact with optical sensor 220 couldundesirably alter the pressure readings measured by optical sensor 220.It may also be desirable to limit distal migration of adhesive 226within shaft 212.

In order to limit distal migration of coating 219 (and/or adhesive 226)within shaft 212, a sealing member 264 may be coupled to fiber opticcable 224. Sealing member 264 may generally take the form of structurethat engages the inner wall of shaft 212 so as to plug or “seal” theinterior of shaft 212. In at least some instances, sealing member 264has a generally conical shape that wedges against the inner surface ofshaft 212. For example, sealing member 264 may include a wedge portion266 that engages the inner surface of shaft 212. Sealing member 264 maybe wedged against the inner surface of shaft 212 by applying a pushingand/or pulling force onto sealing member 264 (e.g., via fiber opticcable 224) so that sealing member 264 is forced against the innersurface of shaft 212. By wedging portion 266 against the inner surfaceof shaft 212, the interior of shaft 212 may be plugged or sealed so thatdistal migration of coating 219 within shaft 212 can be reduced (e.g.,eliminated).

In some instances, sealing member 264 may take the form of an adhesivecone that is attached to centering member 260. For example, sealingmember 264 may be attached to the proximal end of centering member 260and extend proximally therefrom. In other instances, sealing member 264is longitudinally spaced from centering member 260. The entire sealingmember 264 may be conical in shape or, in other instances, sealingmember may include a conical portion. Other shapes are contemplatedincluding shapes that are not conical.

Sealing member 264 may include a suitable material. For example, sealingmember 264 may include an adhesive and/or a UV adhesive (e.g., that maybe cured using a UV LED lamp), a polymer, or the like. For example,sealing member may include DYMAX 204-CTH-T adhesive (commerciallyavailable from Dymax Corporation, Torrington, Conn.). The adhesive maybe cured for a suitable time period (e.g., about 5-60 seconds, or about15-45 seconds, or about 35 seconds) using a suitable UV source (e.g., ablue wave LED lamp). Other adhesives/materials are contemplated.

FIG. 6 illustrates another example guidewire 310 that may be the same inform and function to other guidewires disclosed herein. Guidewire 310includes shaft 312 having proximal region 314 and distal region 316.Shaft 312 has slots 318 formed therein. Coating 319 may be disposedalong the outer surface of shaft 312.

Optical sensor 320 is disposed within distal region 316. In at leastsome instances, a slot or opening (not shown) may be formed in distalregion 316 so as to allow fluid (e.g., blood) to access sensor 320.Fiber optic cable 324 is secured to optical sensor 320 and extendsproximally therefrom. Fiber optic cable 324 may be attached to shaft 312with attachment member/adhesive 326 (e.g., by passing adhesive 326through slot 318 a). Centering member 360 may be secured to fiber opticcable 324. Coating 319 may be disposed along the outer surface of shaft312.

Sealing member 364 may be coupled to fiber optic cable 324. In thisexample, sealing member 364 takes the form of a cylindrical member thatis disposed within and seals against the inner surface of shaft 312 soas to reduce (e.g., prevent) distal migration of coating 319 (and/oradhesive 326) within shaft 312.

The materials that can be used for the various components of guidewire10 (and/or other guidewires 110/210/310 disclosed herein) and thevarious tubular members disclosed herein may include those commonlyassociated with medical devices. For simplicity purposes, the followingdiscussion makes reference to shaft 12 and other components of guidewire10. However, this is not intended to limit the devices and methodsdescribed herein, as the discussion may be applied to other tubularmembers (e.g., shafts 112/212/312) and/or components of tubular membersor devices disclosed herein.

Shaft 12/112/212/312 may be made from a metal, metal alloy, polymer(some examples of which are disclosed below), a metal-polymer composite,ceramics, combinations thereof, and the like, or other suitablematerial. Some examples of suitable metals and metal alloys includestainless steel, such as 304V, 304L, and 316LV stainless steel; mildsteel; nickel-titanium alloy such as linear-elastic and/or super-elasticnitinol; other nickel alloys such as nickel-chromium-molybdenum alloys(e.g., UNS: N06625 such as INCONEL® 625, UNS: N06022 such as HASTELLOY®C-22®, UNS: N10276 such as HASTELLOY® C276®, other HASTELLOY® alloys,and the like), nickel-copper copper alloys (e.g., UNS: N04400 such asMONEL® 400, NICKELVAC® 400, NICORROS® 400, and the like),nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such asMP35-N® and the like), nickel-molybdenum alloys (e.g., UNS: N10665 suchas HASTELLOY® ALLOY B2®), other nickel-chromium alloys, othernickel-molybdenum alloys, other nickel-cobalt alloys, other nickel-ironalloys, other nickel-copper alloys, other nickel-tungsten or tungstenalloys, and the like; cobalt-chromium alloys; cobalt-chromium-molybdenumalloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like);platinum enriched stainless steel; titanium; combinations thereof; andthe like; or any other suitable material.

As alluded to herein, within the family of commercially availablenickel-titanium or nitinol alloys, is a category designated “linearelastic” or “non-super-elastic” which, although may be similar inchemistry to conventional shape memory and super elastic varieties, mayexhibit distinct and useful mechanical properties. Linear elastic and/ornon-super-elastic nitinol may be distinguished from super elasticnitinol in that the linear elastic and/or non-super-elastic nitinol doesnot display a substantial “superelastic plateau” or “flag region” in itsstress/strain curve like super elastic nitinol does. Instead, in thelinear elastic and/or non-super-elastic nitinol, as recoverable strainincreases, the stress continues to increase in a substantially linear,or a somewhat, but not necessarily entirely linear relationship untilplastic deformation begins or at least in a relationship that is morelinear that the super elastic plateau and/or flag region that may beseen with super elastic nitinol. Thus, for the purposes of thisdisclosure linear elastic and/or non-super-elastic nitinol may also betermed “substantially” linear elastic and/or non-super-elastic nitinol.

In some cases, linear elastic and/or non-super-elastic nitinol may alsobe distinguishable from super elastic nitinol in that linear elasticand/or non-super-elastic nitinol may accept up to about 2-5% strainwhile remaining substantially elastic (e.g., before plasticallydeforming) whereas super elastic nitinol may accept up to about 8%strain before plastically deforming. Both of these materials can bedistinguished from other linear elastic materials such as stainlesssteel (that can also can be distinguished based on its composition),which may accept only about 0.2 to 0.44 percent strain beforeplastically deforming.

In some embodiments, the linear elastic and/or non-super-elasticnickel-titanium alloy is an alloy that does not show anymartensite/austenite phase changes that are detectable by differentialscanning calorimetry (DSC) and dynamic metal thermal analysis (DMTA)analysis over a large temperature range. For example, in someembodiments, there may be no martensite/austenite phase changesdetectable by DSC and DMTA analysis in the range of about −60 degreesCelsius (° C.) to about 120° C. in the linear elastic and/ornon-super-elastic nickel-titanium alloy. The mechanical bendingproperties of such material may therefore be generally inert to theeffect of temperature over this very broad range of temperature. In someembodiments, the mechanical bending properties of the linear elasticand/or non-super-elastic nickel-titanium alloy at ambient or roomtemperature are substantially the same as the mechanical properties atbody temperature, for example, in that they do not display asuper-elastic plateau and/or flag region. In other words, across a broadtemperature range, the linear elastic and/or non-super-elasticnickel-titanium alloy maintains its linear elastic and/ornon-super-elastic characteristics and/or properties.

In some embodiments, the linear elastic and/or non-super-elasticnickel-titanium alloy may be in the range of about 50 to about 60 weightpercent nickel, with the remainder being essentially titanium. In someembodiments, the composition is in the range of about 54 to about 57weight percent nickel. One example of a suitable nickel-titanium alloyis FHP-NT alloy commercially available from Furukawa Techno Material Co.of Kanagawa, Japan. Some examples of nickel titanium alloys aredisclosed in U.S. Pat. Nos. 5,238,004 and 6,508,803, which areincorporated herein by reference. Other suitable materials may includeULTANIUM™ (available from Neo-Metrics) and GUM METAL™ (available fromToyota). In some other embodiments, a superelastic alloy, for example asuperelastic nitinol can be used to achieve desired properties.

In at least some embodiments, portions or all of 12/112/212/312 may alsobe doped with, made of, or otherwise include a radiopaque material.Radiopaque materials are understood to be materials capable of producinga relatively bright image on a fluoroscopy screen or another imagingtechnique during a medical procedure. This relatively bright image aidsthe user of guidewire 10/110/210/310 in determining its location. Someexamples of radiopaque materials can include, but are not limited to,gold, platinum, palladium, tantalum, tungsten alloy, polymer materialloaded with a radiopaque filler, and the like. Additionally, otherradiopaque marker bands and/or coils may also be incorporated into thedesign of guidewire 10/110/210/310 to achieve the same result.

In some embodiments, a degree of Magnetic Resonance Imaging (Mill)compatibility is imparted into guidewire 10/110/210/310. For example,12/112/212/312 or portions thereof may be made of a material that doesnot substantially distort the image and create substantial artifacts(i.e., gaps in the image). Certain ferromagnetic materials, for example,may not be suitable because they may create artifacts in an Mill image.Shaft 12, or portions thereof, may also be made from a material that theMill machine can image. Some materials that exhibit thesecharacteristics include, for example, tungsten,cobalt-chromium-molybdenum alloys (e.g., UNS: R30003 such as ELGILOY®,PHYNOX®, and the like), nickel-cobalt-chromium-molybdenum alloys (e.g.,UNS: R30035 such as MP35-N® and the like), nitinol, and the like, andothers.

A sheath or covering (not shown) may be disposed over portions or all of12/112/212/312 that may define a generally smooth outer surface forguidewire 10/110/210/310. In other embodiments, however, such a sheathor covering may be absent from a portion of all of guidewire10/110/210/310, such that 12/112/212/312 may form the outer surface. Thesheath may be made from a polymer or other suitable material. Someexamples of suitable polymers may include polytetrafluoroethylene(PTFE), ethylene tetrafluoroethylene (ETFE), fluorinated ethylenepropylene (FEP), polyoxymethylene (POM, for example, DELRIN® availablefrom DuPont), polyether block ester, polyurethane (for example,Polyurethane 85A), polypropylene (PP), polyvinylchloride (PVC),polyether-ester (for example, ARNITEL® available from DSM EngineeringPlastics), ether or ester based copolymers (for example,butylene/poly(alkylene ether) phthalate and/or other polyesterelastomers such as HYTREL® available from DuPont), polyamide (forexample, DURETHAN® available from Bayer or CRISTAMID® available from ElfAtochem), elastomeric polyamides, block polyamide/ethers, polyetherblock amide (PEBA, for example available under the trade name PEBAX®),ethylene vinyl acetate copolymers (EVA), silicones, polyethylene (PE),Marlex high-density polyethylene, Marlex low-density polyethylene,linear low density polyethylene (for example REXELL®), polyester,polybutylene terephthalate (PBT), polyethylene terephthalate (PET),polytrimethylene terephthalate, polyethylene naphthalate (PEN),polyetheretherketone (PEEK), polyimide (PI), polyetherimide (PEI),polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polyparaphenylene terephthalamide (for example, KEVLAR®), polysulfone,nylon, nylon-12 (such as GRILAMID® available from EMS American Grilon),perfluoro(propyl vinyl ether) (PFA), ethylene vinyl alcohol, polyolefin,polystyrene, epoxy, polyvinylidene chloride (PVdC),poly(styrene-b-isobutylene-b-styrene) (for example, SIBS and/or SIBS50A), polycarbonates, ionomers, biocompatible polymers, other suitablematerials, or mixtures, combinations, copolymers thereof, polymer/metalcomposites, and the like. In some embodiments the sheath can be blendedwith a liquid crystal polymer (LCP). For example, the mixture cancontain up to about 6 percent LCP.

In some embodiments, the exterior surface of the guidewire10/110/210/310 (including, for example, the exterior surface of12/112/212/312) may be sandblasted, beadblasted, sodiumbicarbonate-blasted, electropolished, etc. In these as well as in someother embodiments, a coating, for example a lubricious, a hydrophilic, aprotective, or other type of coating may be applied over portions or allof the sheath, or in embodiments without a sheath over portion of12/112/212/312, or other portions of guidewire 10/110/210/310.Alternatively, the sheath may comprise a lubricious, hydrophilic,protective, or other type of coating. Hydrophobic coatings such asfluoropolymers provide a dry lubricity which improves guidewire handlingand device exchanges. Lubricious coatings improve steerability andimprove lesion crossing capability. Suitable lubricious polymers arewell known in the art and may include silicone and the like, hydrophilicpolymers such as high-density polyethylene (HDPE),polytetrafluoroethylene (PTFE), polyarylene oxides,polyvinylpyrolidones, polyvinylalcohols, hydroxy alkyl cellulosics,algins, saccharides, caprolactones, and the like, and mixtures andcombinations thereof. Hydrophilic polymers may be blended amongthemselves or with formulated amounts of water insoluble compounds(including some polymers) to yield coatings with suitable lubricity,bonding, and solubility. Some other examples of such coatings andmaterials and methods used to create such coatings can be found in U.S.Pat. Nos. 6,139,510 and 5,772,609, which are incorporated herein byreference.

The coating and/or sheath may be formed, for example, by coating,extrusion, co-extrusion, interrupted layer co-extrusion (ILC), or fusingseveral segments end-to-end. The layer may have a uniform stiffness or agradual reduction in stiffness from the proximal end to the distal endthereof. The gradual reduction in stiffness may be continuous as by ILCor may be stepped as by fusing together separate extruded tubularsegments. The outer layer may be impregnated with a radiopaque fillermaterial to facilitate radiographic visualization. Those skilled in theart will recognize that these materials can vary widely withoutdeviating from the scope of the present invention.

Various embodiments of arrangements and configurations of slots are alsocontemplated that may be used in addition to what is described above ormay be used in alternate embodiments. For simplicity purposes, thefollowing disclosure makes reference to guidewire 10, slots18/118/218/318, and shaft 12/112/212/312. However, it can be appreciatedthat these variations may also be utilized for other slots (e.g., slits118, slots 218, slots 318) and/or tubular members (e.g., shafts112/212/312). In some embodiments, at least some, if not all of slots18/118/218/318 are disposed at the same or a similar angle with respectto the longitudinal axis of shaft 12/112/212/312. As shown, slots18/118/218/318 can be disposed at an angle that is perpendicular, orsubstantially perpendicular, and/or can be characterized as beingdisposed in a plane that is normal to the longitudinal axis of shaft12/112/212/312. However, in other embodiments, slots 18/118/218/318 canbe disposed at an angle that is not perpendicular, and/or can becharacterized as being disposed in a plane that is not normal to thelongitudinal axis of shaft 12/112/212/312. Additionally, a group of oneor more slots 18/118/218/318 may be disposed at different anglesrelative to another group of one or more slots 18/118/218/318. Thedistribution and/or configuration of slots 18/118/218/318 can alsoinclude, to the extent applicable, any of those disclosed in U.S. Pat.Publication No. US 2004/0181174, the entire disclosure of which isherein incorporated by reference.

Slots 18/118/218/318 may be provided to enhance the flexibility of shaft12/112/212/312 while still allowing for suitable torque transmissioncharacteristics. Slots 18/118/218/318 may be formed such that one ormore rings and/or tube segments interconnected by one or more segmentsand/or beams that are formed in shaft 12/112/212/312, and such tubesegments and beams may include portions of shaft 12/112/212/312 thatremain after slots 18/118/218/318 are formed in the body of shaft12/112/212/312. Such an interconnected structure may act to maintain arelatively high degree of torsional stiffness, while maintaining adesired level of lateral flexibility. In some embodiments, some adjacentslots 18/118/218/318 can be formed such that they include portions thatoverlap with each other about the circumference of shaft 12/112/212/312.In other embodiments, some adjacent slots 18/118/218/318 can be disposedsuch that they do not necessarily overlap with each other, but aredisposed in a pattern that provides the desired degree of lateralflexibility.

Additionally, slots 18/118/218/318 can be arranged along the length of,or about the circumference of, shaft 12/112/212/312 to achieve desiredproperties. For example, adjacent slots 18/118/218/318, or groups ofslots 18/118/218/318, can be arranged in a symmetrical pattern, such asbeing disposed essentially equally on opposite sides about thecircumference of shaft 12/112/212/312, or can be rotated by an anglerelative to each other about the axis of shaft 12/112/212/312.Additionally, adjacent slots 18/118/218/318, or groups of slots18/118/218/318, may be equally spaced along the length of shaft12/112/212/312, or can be arranged in an increasing or decreasingdensity pattern, or can be arranged in a non-symmetric or irregularpattern. Other characteristics, such as slot size, slot shape, and/orslot angle with respect to the longitudinal axis of shaft12/112/212/312, can also be varied along the length of shaft12/112/212/312 in order to vary the flexibility or other properties. Inother embodiments, moreover, it is contemplated that the portions of thetubular member, such as a proximal section, or a distal section, or theentire shaft 12/112/212/312, may not include any such slots18/118/218/318.

As suggested herein, slots 18/118/218/318 may be formed in groups oftwo, three, four, five, or more slots 18/118/218/318, which may belocated at substantially the same location along the axis of shaft12/112/212/312. Alternatively, a single slot 18 may be disposed at someor all of these locations. Within the groups of slots 18/118/218/318,there may be included slots 18/118/218/318 that are equal in size (i.e.,span the same circumferential distance around shaft 12/112/212/312). Insome of these as well as other embodiments, at least some slots18/118/218/318 in a group are unequal in size (i.e., span a differentcircumferential distance around shaft 12/112/212/312). Longitudinallyadjacent groups of slots 18/118/218/318 may have the same or differentconfigurations. For example, some embodiments of shaft 12/112/212/312include slots 18/118/218/318 that are equal in size in a first group andthen unequally sized in an adjacent group. It can be appreciated that ingroups that have two slots 18/118/218/318 that are equal in size and aresymmetrically disposed around the tube circumference, the centroid ofthe pair of beams (i.e., the portion of shaft 12/112/212/312 remainingafter slots 18/118/218/318 are formed therein) is coincident with thecentral axis of shaft 12/112/212/312. Conversely, in groups that havetwo slots 18/118/218/318 that are unequal in size and whose centroidsare directly opposed on the tube circumference, the centroid of the pairof beams can be offset from the central axis of shaft 12/112/212/312.Some embodiments of shaft 12/112/212/312 include only slot groups withcentroids that are coincident with the central axis of the shaft12/112/212/312, only slot groups with centroids that are offset from thecentral axis of shaft 12/112/212/312, or slot groups with centroids thatare coincident with the central axis of shaft 12/112/212/312 in a firstgroup and offset from the central axis of shaft 12/112/212/312 inanother group. The amount of offset may vary depending on the depth (orlength) of slots 18/118/218/318 and can include other suitabledistances.

Slots 18/118/218/318 can be formed by methods such as micro-machining,saw-cutting (e.g., using a diamond grit embedded semiconductor dicingblade), electron discharge machining, grinding, milling, casting,molding, chemically etching or treating, or other known methods, and thelike. In some such embodiments, the structure of the shaft12/112/212/312 is formed by cutting and/or removing portions of the tubeto form slots 18/118/218/318. Some example embodiments of appropriatemicromachining methods and other cutting methods, and structures fortubular members including slots and medical devices including tubularmembers are disclosed in U.S. Pat. Publication Nos. 2003/0069522 and2004/0181174-A2; and U.S. Pat. Nos. 6,766,720; and 6,579,246, the entiredisclosures of which are herein incorporated by reference. Some exampleembodiments of etching processes are described in U.S. Pat. No.5,106,455, the entire disclosure of which is herein incorporated byreference. It should be noted that the methods for manufacturingguidewire 10/110/210/310 may include forming slots 18/118/218/318 inshaft 12/112/212/312 using these or other manufacturing steps.

In at least some embodiments, slots 18/118/218/318 may be formed intubular member using a laser cutting process. The laser cutting processmay include a suitable laser and/or laser cutting apparatus. Forexample, the laser cutting process may utilize a fiber laser. Utilizingprocesses like laser cutting may be desirable for a number of reasons.For example, laser cutting processes may allow shaft 12/112/212/312 tobe cut into a number of different cutting patterns in a preciselycontrolled manner. This may include variations in the slot width, ringwidth, beam height and/or width, etc. Furthermore, changes to thecutting pattern can be made without the need to replace the cuttinginstrument (e.g., blade). This may also allow smaller tubes (e.g.,having a smaller outer diameter) to be used to form shaft 12/112/212/312without being limited by a minimum cutting blade size. Consequently,shaft 12/112/212/312 may be fabricated for use in neurological devicesor other devices where a relatively small size may be desired.

It should be understood that this disclosure is, in many respects, onlyillustrative. Changes may be made in details, particularly in matters ofshape, size, and arrangement of steps without exceeding the scope of theinvention. This may include, to the extent that it is appropriate, theuse of any of the features of one example embodiment being used in otherembodiments. The invention's scope is, of course, defined in thelanguage in which the appended claims are expressed.

What is claimed is:
 1. A medical device for measuring blood pressure,comprising: an elongated shaft having a proximal region and a distalregion; an optical fiber extending along the proximal region; whereinthe optical fiber is secured to an inner surface of the shaft; anoptical pressure sensor coupled to the optical fiber, the opticalpressure sensor being disposed along the distal region; a centeringmember coupled to the optical fiber and positioned adjacent to theoptical pressure sensor; and a sealing member attached to the centeringmember and extending proximally therefrom, the sealing member having asurface engaged with the inner surface of the shaft.
 2. The medicaldevice of claim 1, wherein the sealing member is secured to a proximalend of the centering member.
 3. The medical device of claim 1, whereinthe sealing member includes a conical portion.
 4. The medical device ofclaim 3, wherein the conical portion is wedged against the inner surfaceof the shaft.
 5. The medical device of claim 1, wherein the sealingmember includes a cylindrical section.
 6. The medical device of claim 5,wherein the cylindrical section contacts the inner surface of the shaft.7. The medical device of claim 1, wherein the shaft includes an outercoating.
 8. The medical device of claim 7, wherein the sealing member isdesigned to limit distal migration of the coating within the shaft. 9.The medical device of claim 1, wherein the shaft has a plurality ofslots formed therein.
 10. The medical device of claim 1, wherein thedistal region of the shaft has a distal inner diameter, wherein theproximal region of the shaft has a proximal inner diameter, and whereinthe distal inner diameter is larger than the proximal inner diameter.11. The medical device of claim 10, wherein the sealing member ispositioned at a transition region between the proximal region and thedistal region.
 12. The medical device of claim 1, wherein the medicaldevice is a guidewire for measuring fractional flow reserve.
 13. Amedical device for measuring blood pressure, comprising: a tubularmember having a proximal region, a distal region, and a sensor housingregion; a coating disposed along an outer surface of the tubular member;wherein the tubular member has a plurality of slots formed therein; anoptical fiber extending along the proximal region; an optical pressuresensor coupled to the optical fiber, the optical pressure sensor beingdisposed within the sensor housing region; and a sealing member attachedto the optical fiber, the sealing member being disposed within thesensor housing region and having a surface extending into and engagedwith the inner surface of the tubular member along the distal region soas to limit distal migration of the coating within the tubular member.14. The medical device of claim 13, wherein the sealing member includesa conical portion that is wedged against the inner surface of thetubular member.
 15. The medical device of claim 13, wherein the sealingmember includes a cylindrical section that contacts the inner surface ofthe tubular member.
 16. The medical device of claim 13, furthercomprising a centering member coupled to the optical fiber andpositioned adjacent to the optical pressure sensor and wherein thesealing member is secured to a proximal end of the centering member. 17.The medical device of claim 13, wherein the distal region of the tubularmember has a distal inner diameter, wherein the proximal region of thetubular member has a proximal inner diameter, wherein the distal innerdiameter is larger than the proximal inner diameter, and wherein thesealing member is positioned at a transition region between the proximalregion and the distal region.
 18. A method for manufacturing a medicaldevice, the method comprising: disposing an optical fiber within atubular member, wherein: a coating is disposed along an outer surface ofthe tubular member, the tubular member has a proximal region and adistal region, the distal region has a distal inner diameter, theproximal region has a proximal inner diameter that is smaller than thedistal inner diameter, the distal region, the proximal region, or bothhave a plurality of slots formed therein, and an optical pressure sensorcoupled to the optical fiber, the optical pressure sensor being disposedwithin the distal region of the tubular member; disposing a sealingmember within the distal region of the tubular member, the sealingmember having a proximally-extending surface engaged with an innersurface of the proximal region of the tubular member; and wherein thesealing member is designed to limit distal migration of the coatingwithin the tubular member.
 19. The method of claim 18, wherein thesealing member has a conical portion and wherein disposing a sealingmember within the distal region of the tubular member includes wedgingthe conical portion of the sealing member against the inner surface ofthe proximal region of the tubular member.